1. Field of the Invention
The present invention generally relates to an apparatus and method for burning fuel and, more particularly, to an apparatus and method of burning fuel in a combustion chamber.
2. Description of Prior Art
As is well known, plant matter contains volatile contents which vaporize or volatilize readily at relatively low temperatures. This makes plant matter, such as wood, well suited to be used as fuel, because it burns easily. One particular form of wood that is used industrially for fuel is wood pellets. Such pellets are formed by heating wood and compressing it under pressure. Two common types of pelletized wood are pine and cedar wood. Pine and cedar, and particularly their barks are especially good fuels because they contain large amounts of volatile contents.
It has been discovered that the percentage of a wood pellet that varporizes or volatilizes can be increased by placing the pellet in a high temperature environment at 800.degree. C., either prior to or during combustion. 1. Furthermore, it is discovered that the quantity of the gas to be generated by volatilization, such as methane and ethylene, is also increased. This discovery is important because the more fuel that is vaporized or volatilized, the greater the heat that is released 4. , as well as the amount of gas to be generated then. Thus, the combustion of fuel containing volatile contents can be m,de more efficient by heating or preheating the fuel to 800.degree. C.
According to an experiment conducted by the present inventor, 73% of a given amount of pine bark when heated in a high temperature atmosphere of 800.degree. C., 2. with the other factors than temperature being maintained at a certain level vaporized or volatilized; the remainder of the pine was 2.2% ash content and 24.6% fixed carbon. 3. in addition, the quantity of methane and ethylene to be generated when heated at 800.degree. C. is 10 times and 36 times as large, respectively, compared to when heated at 400.degree. C.
A typical furnace burner produces a combustion flame that contains a zone of heat in the flame that is 800.degree. C.
When left undisturbed, this 800.degree. C. zone of heat, called the zone of volatilization, maintains a stable position, enveloping the fuel on the burner. However, conventional boilers and combustion chambers are constructed in a manner which results in the combustion flame being disturbed and unstable, thereby moving the zone of volatilization away from the fuel. Conventional combustion chambers, such as that disclosed by U.S. Pat. No. 4,007,697, typically position an exhaust port at one corner or one side wall at the upper portion of the combustion chamber. As a result, the combustion flame flares toward the exhaust port causing an unstable flame configuration. This causes the zone of volatilization to become unstable and move away from the fuel, thereby decreasing the amount of fuel that is vaporized and burned. There is, therefore, a need for a combustion chamber that allows the flame configuration to be stable, and thereby permits the zone of volatilization to continuously envelope the fuel.